In the sequencing batch reactor process of waste water treatment, a basin or reactor is operated in a batch treatment mode involving a fill phase, a react phase, a settle phase, and a decant phase. Depending upon the treatment requirement of the specific SBR design, the fill cycle may be composed of static-fill, mix-only-fill, as well as react-fill phases. Under static fill, influent flow is introduced to the reactor under a non-mixed, non-aerated environment. A mix-fill phase provides reactor mixing without aeration, and react-fill and the react phases involve both mixing and aeration. The suspended solids are allowed to settle during the settle phase, and the relatively clear effluent is withdrawn from the reactor during the decant phase. The duration and timing of the several phases varies in different installations and some of the phases can overlap.
Sequencing batch reactor systems, hereinafter referred to as SBR systems, have heretofore employed a plurality of separate apparatus which are individually installed in the reactor basin. For example, some prior SBR systems made by the assignee of the present invention used a floating downflow mixer of the type disclosed in U.S. Pat. No. 4,422,771; aerator means either of the floating spray type disclosed in U.S. Pat. No. 3,606,273 or the submerged air diffuser type; and a floating decanter of the type disclosed in U.S. Pat. No. 4,695,376. The mixer, aerator and decanter were individually installed in the reactor basin and operated under an SBR program controller which would operate the mixer, aerator and decanter during the appropriate phases of the SBR process. It has also been proposed, for example as disclosed in U.K. Patent 1,428,349 published Mar. 17, 1976, to provide a down-flow mixer with an aspirator nozzle to aspirate air into the liquid pump of the downflow mixer.